refactor dda

1 files changed, 7 insertions, 33 deletions

diff --git a/src/sim/particle_sim/mod.rs b/src/sim/particle_sim/mod.rs
index 08febfb..4378d25 100644
--- a/src/sim/particle_sim/mod.rs
+++ b/src/sim/particle_sim/mod.rs
@@ -8,6 +8,7 @@ use crate::{
             materials::{MaterialForm, MaterialId},
         },
         cell_sim::world::World,
+        lib::ray::AwDda,
         particle_sim::particle::Particle,
     },
 };
@@ -35,46 +36,20 @@ impl ParticleManager {
             p.velocity.y += PARTICLE_GRAVITY * delta_time;
             let dt_velocity = p.velocity * delta_time;
 
-            // Amanatides and Woo's fast Voxel Traversal
-            {
-                let mut cur = IVec2::new(p.position.x.round() as i32, p.position.y.round() as i32);
-                // direction we step for each component on each iteration
-                let step_sign =
-                    IVec2::new(dt_velocity.x.signum() as i32, dt_velocity.y.signum() as i32);
-                let delta = Vec2::new(1.0 / dt_velocity.x.abs(), 1.0 / dt_velocity.y.abs());
+            let mut dda = AwDda::new(p.position, p.position + p.velocity * delta_time);
 
-                let frac = Vec2::new(
-                    if step_sign.x > 0 {
-                        (cur.x as f32 + 0.5) - p.position.x
-                    } else {
-                        p.position.x - (cur.x as f32 - 0.5)
-                    },
-                    if step_sign.y > 0 {
-                        (cur.y as f32 + 0.5) - p.position.y
-                    } else {
-                        p.position.y - (cur.y as f32 - 0.5)
-                    },
-                );
-                let mut t_max = frac * delta;
-
-                let mut prev = cur;
+            if let Some(prev) = dda.next() {
                 if let Some(cell) = world.get_cell_from_game_position(prev.x, prev.y)
                     && [MaterialForm::Solid, MaterialForm::Powder]
                         .contains(&cell.material.def().form)
                 {
-                    // already occupied, die
+                    // the particle is already inside a collider, we should just kill it
                     self.particles.swap_remove(i);
                     continue 'outer;
                 }
-                while t_max.min_element() <= 1.0 {
-                    if t_max.x < t_max.y {
-                        cur.x += step_sign.x;
-                        t_max.x += delta.x;
-                    } else {
-                        cur.y += step_sign.y;
-                        t_max.y += delta.y;
-                    }
-                    if let Some(cell) = world.get_cell_from_game_position(cur.x, cur.y)
+
+                for cell in dda.map(|p| world.get_cell_from_game_position(p.x, p.y)) {
+                    if let Some(cell) = cell
                         && [MaterialForm::Solid, MaterialForm::Powder]
                             .contains(&cell.material.def().form)
                     {
@@ -88,7 +63,6 @@ impl ParticleManager {
                         self.particles.swap_remove(i);
                         continue 'outer;
                     }
-                    prev = cur;
                 }
             }